1. Field of the Invention
The present invention relates to a diamond film synthesizing technology by chemical vapor deposition (CVD).
2. Description of the Background Art
Diamond can be synthesized by high pressure and high temperature (HPHT), detonation and chemical vapor deposition (CVD) methods.
The HPHT method of which condition is 1500° C. of temperature and 50,000 atmosphere of pressure enables us to synthesize grit-type diamonds where sizes are below hundreds pm in diameter or irregular shaped diamond powders in the micrometer range in size. Nanometer scale diamond powders can be synthesized by the detonation method of which condition is 1000° C. of temperature and 300,000 atmosphere of pressure. A typical shape of diamond synthesized under HPHT methods including the detonation method is a powder (or particle) type.
On the other hand, CVD method of which condition is around 700° C. of temperature and around 40-200 Torr of pressure deposits diamond onto substrates (or matrix), normally silicon wafers. CVD diamond also can be coated on curved substrate such as drills and inserts. During deposition, the substrates are placed on a plate or held in a stage. Freestanding diamond films can be prepared if the substrate is removed by etching.
However, CVD method cannot deposit diamond films on whole surfaces of substrates because a part of a substrate is in contact with a plate or a stage where diamond deposition is not available. Also, hollow diamond shells have never been prepared with previous arts yet.